1. Field of the Invention
This invention relates to a dishwasher pump and more particularly to a dishwasher pump that reduces pump noise associated with the recirculation cycle and pump noise and sink/disposer splashing associated with the drain cycle.
2. Description of the Prior Art
It is common in some dishwasher pumps to include two pumping chambers with two impellers connected to a common shaft. In the recirculating mode, the impellers are both rotated in one direction thereby recirculating the washing fluid within the washing chamber. In the drain mode, both impellers are rotated in the opposite sense.
During recirculation, noise is often created in the recirculating pump by air pockets contained in the fluid striking the pump's impeller. In addition, the drain pump, although it does not operate efficiently, still attempts to pump fluid out of the appliance thereby creating a pressure head in the drain outlet.
During the drain cycle, fluid can be pumped out under great pressure causing splash at the end of the drain line. Towards the end of the drain cycle there is only a little fluid, known as a slug, left to be pumped out. The slug is pumped out into the drain outlet followed by a pocket of air. The slug travels up the drain line formed as a vertical loop alongside the dishwasher and then gravity pulls the slug back into the pump where it strikes the pump impeller thereby creating noise. This continues in a rhythmic pattern as the pump continues to propel the slug of fluid up the drain line.
There are pumps in the prior art that eliminate noise in a recirculation pump during the drain cycle and in the drain pump during the recirculation cycle. U.S. Pat. No. 3,294,102 (Ruspino et al) discloses a way of eliminating noise created in the recirculation pump during the drain cycle. The noise is created by the impeller blades of the recirculation pump which will cavitate and produce high shear forces on the water left in the recirculation pump housing causing impact on the impeller and housing. A vent is added to draw air into the impeller area of the housing of the recirculation pump thereby pushing the washing fluid away from the impeller. U.S. Pat. No. 3,353,553 (Lind et al) eliminates noise in the drain pump during recirculation by introducing air into the drain pump via an air line controlled by a valve. The air displaces any fluid that is in the drain pump during recirculation. U.S. Pat. No. 4,355,954 (Wilson) discloses a recirculation pump impeller having a modified vane structure. During the drain cycle, the fluid left in the recirculation pump mixes with air and causes a turbulent flow in the pump outlet area creating noise. The modified vane structure eliminates this noise.
None of these references eliminate noise in the recirculation pump during recirculation or noise in the drain pump during the drain cycle.
U.S. Pat. No. 3,324,796 (LaFlame) discloses a dishwasher wherein a portion of the drain pumping chamber is vented to atmosphere by vacuum breaking means. During the recirculation mode, the drain pump draws waste fluid from the looped drain into the sump. The vacuum breaking means keeps the drain outlet at atmospheric pressure during those periods thus inhibiting the drain pump from drawing fluid from the looped drain into the sump.
U.S. Pat. No. 4,753,570 (Jarvis) discloses a dishwasher pump having one impeller chamber communicating with both a conduit for delivering washing fluid and a conduit for draining the fluid. An opening between the wash conduit and the drain conduit is controlled by a diaphragm valve determining the direction of fluid flow.
The prior art does not disclose the advantages of the present invention. The present invention minimizes noise in the recirculation pump during recirculation and noise in the drain pump during drainage.
In addition, the present invention reduces the pressure in the drain line during recirculation thereby lowering the pressure head in the drain line.
Also, the present invention reduces the output pressure in the drain line during drainage thereby slowing the pump-out rate and reducing the likelihood of splash at the end of the drain line.